Forest Pests: Insects, Diseases & Other Damage Agents

Lesser pine shoot beetle - Tomicus minor (Hart.)

From: Kolk A., Starzyk J. R., 1996: The Atlas of Forest Insect Pests
(Atlas skodliwych owadów lesnych) - Multico Warszawa, 705 pages. Original publication in Polish. English translation provided by Dr. Lidia Sukovata and others under agreement with The Polish Forest Research Institute.

Occurrence: Europe, the northern Asia, China, Taiwan, Korea, Japan.

Host plants: The Scots pine and other pine species.

Morphology: Adults are 3.0 - 4.5 mm long, similar to T. piniperda, shiny, black with reddish-brown elytrae, antennae and feet. Elytral declivity is without grooves, which are present in T. piniperda.

Biology: Adults overwinter in litter or pine shoots. They initiate flying in late-March and early-April at temperatures about 12oC. After mating, females construct horizontal bird-shaped egg galleries (up to 12 cm long and 2 mm wide) mainly under the thin bark on standing trees. These galleries are well visible in the outer sapwood. One female lays about 100 eggs. After hatching, larvae construct vertical feeding galleries (2-5 cm long) that go perpendicularly to maternal ones and along the fiber. Larvae pupate quite deeply in the sapwood. The newly-formed adults emerge in late-July - early-August. Young and old adults have supplementary feeding inside the pine shoots.

Damage: T. minor infests weakened standing trees, mainly their upper part with the thin bark and branches. Feeding during the reproduction phase is more harmful for a tree than feeding of T. piniperda, because egg galleries go across the fibers deeply in the sapwood, thus leading to the death of the tree top. Attacked trees are later attacked by other species like A. aedilis, Sirex spp., etc. Besides, various species of blue stain fungi are associated with this bark beetle. Supplementary feeding of adults can also be of high importance. This species can be a serious pest in stands of middle age classes, weakened by root fungi or planted on post-agricultural lands. At high population densities it can cause reduction of tree height and diameter growth.

Preventive measures: Removal all potential material suitable for infestation such as: timber, weakened trees, windthrows etc. from the forest in the period from October through March. The tops and branches of cut trees should not be left in the stands with high population density of this insect.

Control: There are several possible control methods:

• the use of trap trees (with tops) in the period from December through March only in stands with high infestation risk due to Tomicus spp. Traps should be debarked before pupation;
• searching for, cutting and removing all infested trees with adults from a woodland in the period from April through August;
• debarking of infested trees and traps. Debarking is not required, if trap trees will be removed from a woodland and/or utilized during 3 weeks after flight initiation.

Diagram, Adult and galleries, Poland Image by Robert Dzwonkowski	Damage, Boring dust Image by Stanislaw Kinelski
Damage, Note horizontal feeding galleries and exit holes Image by Stanislaw Kinelski	Galleries, Switzerland Image by Stanislaw Kinelski

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